Abstract

In spite of the extensive area of bogs in the southern cone of South America, there have been very few studies on structure and dynamics of conifer bog forests in this region. Previously, it has been assumed that in the absence of intensive disturbance, the dominant conifer Pilgerodendron uviferum (D. Don) Florin would be replaced through other angiosperm species. Here we hypothesized (a) that this conifer can persist without intensive disturbances and develop into old-growth forests with continuing regeneration and (b) that high-severity disturbances through fire threaten its local persistence. To test this hypotheses, we analyzed diameter and age structure, foliar and soil nutrient levels and the light environment of old-growth and fire-disturbed P. uviferum stands on Chiloé Island (43ºS) in North Patagonia. Longevity (>880 years), extremely slow growth (<1 mm diameter per year) and tolerance to shade and stress are the main mechanisms of P. uviferum persistence in nutrient-poor and waterlogged conditions. Hence, old-growth P. uviferum forests are not a transitional phase in forest succession and may be maintained in the landscape for many centuries or millennia. However, in fire-disturbed stands, live trees of the species were rare and regeneration negligible, showing that high-severity fires can eliminate the species from parts of the landscape, where neither propagules nor seed trees survive. This underpins the importance of biological legacies such as seed trees for the recovery of disturbed sites, and points to the need for active restoration approaches to restore fire-degraded P. uviferum forests.

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Author Contributions

Jan R. Bannister conceived, designed and performed the research, analyzed the data and wrote the paper. Pablo J. Donoso helped with the design of the research and writing. Jürgen Bauhus conceived and designed the research and helped with data analysis and writing.

Notes

Acknowledgments

We are especially grateful to the administration and staff of the Tantauco Park for constant help and support in the field. N. Carrasco, R. Ramirez, G. Löffler, J. Flade and D. Rieck assisted under difficult conditions in the field. Without their help this study could not have been done. For assistance in the laboratory we thank R. Nitschke, N. Briggs, G. Löffler and M. Schmidt. D. Forrester, T. Kahl and H. Stark helped with statistical analyses. Jan Bannister received a DAAD-CONICYT scholarship to support his PhD studies at the University of Freiburg, where he participated in the graduate school “Environment, Society and Global Change”. This research was also financially supported through grants by the Georg-Ludwig-Hartig and Futuro foundations.